1. Field Of The Invention
The present invention, called a xe2x80x9cbrain stethoscopexe2x80x9d, relates to a medical apparatus and more particularly to a portable EEG (electroencephalograph) device to detect, amplify and analyze brain waves generated by a human and to transmit the results to a remote receiver.
2. Related Art
It has become evident that human brain electrical activity is precisely regulated by a complex brain homeostatic system. Normative values are precisely predictable and have been found to be independent of ethnic factors. Characteristic patterns of deviation from such normative values have been reported for a wide variety of developmental, neurological and psychiatric disorders.
At the present time it is difficult for emergency personnel to determine if a subject has suffered injury to the brain or the spinal cord, cerebrovascular obstruction (stroke) or hemorrhage (bleeding). If these conditions could immediately be identified, patients"" lives may be saved through rapid and appropriate treatment, usually determined after a subsequent neurological exam. The causes of abnormal behavior such as violent outbursts are often similarly ambiguous.
It is usual, during a routine medical examination, to evaluate the heart using an EKG (electrocardiogram) device. Usually, there is no attempt to determine if the patient has any brain dysfunction or conditions that may be discoverable using an EEG (electroencephalograph), as generally such devices produce an analog wavy set of waveshape tracings which must be interpreted subjectively by skilled electroencephalographers. Consequently, although the patient may be suffering from brain damage or dysfunction, such as a tumor, it is often not detected in the course of the medical examination. The absence of information about central nervous system (CNS) dysfunction often results in suboptimal treatment.
As an example, a patient arrives at a hospital emergency room (ER) with certain physical symptoms of ischemic stroke, or xe2x80x9cbrain attackxe2x80x9d, resulting from blocked blood flow to the brain. Unless the patient is treated promptly, brain cells in the ischemic region would continue to be deprived of oxygen, possibly destroying parts of his cognitive abilities, memory and motor skills and possibly resulting in death. Such adverse effects of ischemic stroke may be halted by immediate and appropriate treatment, for example, injection of tissue plasminogen actuator (tPA), which dissolves clots. However, tPA treatment of a possible stroke victim may be hazardous to initiate, as his physical symptoms may be caused by an intracerebral hemorrhage which can be worsened by dissolving clots. Quantitative analysis of the EEG (QEEG) may provide a rapid and objective diagnosis between these alternatives.
As another example, a person may be in a coma when emergency ambulance personnel (EMS) arrive. He should not be moved if he has suffered spinal injury. But the ambulance personnel cannot determine if he has suffered spinal injury by simply looking at the comatose patient. Somatosensory evoked potentials (SEPs) provide assessment of the functional integrity of the spinal cord.
Another example of the need for an objective and immediate brain assessment is in situations where there are a number of injured persons who may require medical attention, some of whom may be in a coma. For example, on the battlefield or in the event of a train wreck, it may be necessary to separate comatose patients who are breathing and viable and require immediate treatment, from those who are still breathing but are brain dead. And again, in that situation, it is important to tell if a patient who is comatose but alive has a spinal injury, so that he should not be moved. QEEG, SEPs and brainstem auditory evoked response (BAERs) may provide a rational basis for triage in such situations.
A series of publications and patents in the name of Dr. E. Roy John relate to the field of EEG xe2x80x9cneurometricsxe2x80x9d, which is quantitative electrophysiological measurements (QEEG) evaluated relative to normative data. Generally, a subject""s analog brain waves, at the microvolt level, are amplified, artifacts removed and the amplified brain waves converted to digital data. That data is then analyzed in a computer system to extract numerical descriptors which are compared to a set of norms (reference values), either the subject""s own prior data (initial state) or a group of normal subjects of the same age (population norm). Such analyses can quantify the level, if any, of deviation of the activity of any brain region from the reference values.
A computer system based instrument using those principles is the xe2x80x9cSpectrum 32xe2x80x9d(Cadwell Instruments, Washington). That instrument is large, non-portable and relatively expensive (tens of thousands of dollars). It is generally used by experienced neurologists in a neurology clinic or hospital neurology department. It is not suitable for use in an ambulance, emergency room or a doctor""s office for regular medical examinations. Some of the aforementioned patents which relate to neurometrics are U.S. Pat. Nos. 4,279,258; 4,846,190; 4,913,160; 5,083,571 and 5,287,859, incorporated by reference.
There are a number of patents directed to determine whether a person is alive. For example, Allain U.S. Pat. No. 5,029,590 discloses the use of a pocket-size monitor for life detection. The Allain patent deals primarily with detecting heartbeat via EKG and mentions detecting brain waves using EEG.
In John U.S. Pat. No. 3,706,308 entitled xe2x80x9cLife Detecting Medical Instrumentxe2x80x9d a portable device has EKG and EEG monitors, a stimulator for evoked brain responses (Evoked Potentialxe2x80x94EP), an average response computer and a visual display. It determines if a patient is legally dead by comparison of the patient""s brain waves with predetermined standards of brain death and does not use comparisons with normal values.
There is an existing need for a portable self-evaluating EEG and EP device which can be monitored by a hand-held control distant from the patient. For example, where an injured person""s heartbeat cannot be detected or he is in a coma, he may be taken to a hospital, which has an EEG device and neurologist to detect and evaluate brain waves and to determine whether he is alive and whether his brain is injured. However, in some emergencies, medical personnel need to quickly determine if a patient has had a stroke or if the patient is alive but in a coma, or dead, or if a person has suffered spinal injury. A particular difficulty arises when some patients have spinal injury and are unconscious. In those cases, it would be difficult for medical personnel to ascertain who can safely be moved or should not be moved because of spinal injury. Persons with such conditions may die due to the lack of medical information, for example, a non-spinal injury patient may be in a coma and is not properly and timely transported to a hospital, or may become paralyzed if moved with unrecognized spinal injury.
In general, there are numerous instances in which the ability to make a xe2x80x9cbrain scanxe2x80x9d by a portable EEG/EP device (xe2x80x9cBrain Stethoscopexe2x80x9d) could be valuable in assessing the probability of abnormal brain function rapidly and automatically.
In accordance with the present invention, there is provided a portable EEG device which can accurately, reliably, continuously and quickly determine if the patient is in a coma, is suffering from concussion or is brain dead; if he is having an ischemic stroke or an intracerebral hemorrhage; if he has a serious spinal injury; and, if his behavior is of concern, whether he has abnormal brain function.
In one embodiment of the present invention, called xe2x80x9cVersion 1xe2x80x9d, intended especially for use by emergency personnel and emergency vehicles, in hospital emergency rooms and family physician offices, an EEG device has a limited number of EEG electrodes and may have an EKG electrode, preferably lead 2, and may receive input from a blood pressure device, such as a finger plethysomometer or blood oxygen or saturation meter. Depending upon the particular application, arrays of 1-16 head electrodes may be used, as compared to the International 10/20 system of 19-21 head electrodes generally used in a conventional EEG instrument. The device is small, prefer ably hand-held, and relatively simple, easy to use and inexpensive. It includes a software programmed microprocessor having a CPU (Central Processor Unit) which performs the following functions: (i) it steps (polls) through the EEG electrodes if more than one electrode is used, so that each symmetrical pair of electrodes (e.g., P3 and P4) is connected simultaneously (electrode pairs are polled in sequence and the instrument is a two-channel or four-channel device) and evaluates the spontaneous EEG; (ii) it provides a timed sequence of concurrent stimulations in one or two sensory modalities (modes) to the patient, such as an audio tone or click at one repetition rate (F1) and electrical shocks to peripheral nerves at a second repetition rate (F2); (iii) based on the responses to these multimodal stimulations, it tests the functional state of the spinal cord (SSEPxe2x80x94Somatosensory Evoked Response) and brain stem (Brain Stem Auditory Evoked Responsexe2x80x94BAER); and (iv) it assesses the cardiac rhythm.
Preferably, stimulations are used in two different modes, i.e., auditory clicks and electric pulses to the skin. The stimuli, although concurrent, are at different prime number frequencies to permit separation of different EPs and avoid interference. Such concurrent stimulations for EP permit a more rapid, and less costly, examination and provide the patient""s responses more quickly, which is important in emergency situations. Power spectra of spontaneous EEG, waveshapes of Averaged Evoked Potentials, and extracted measures, such as frequency specific power ratios, can be transmitted to a remote receiver. The latencies of successive EP peaks of the patient may be compared to those of a normal group by use of a normative template.
Preferably, to test for ischemic stroke or intracerebral or subarachnoid hemorrhage, the instrument includes a blood oxygen saturation monitor, using an infra-red or laser source, to alert the user if the patient""s blood in the brain or some brain region is deoxygenated.
Another embodiment, called xe2x80x9cVersion 2xe2x80x9d, is particularly for use in field conditions in which an immediate indication of brain damage is desired from a number of persons, some of whom may be unconscious. An adhesive patch, or headband, is placed on each subject. It contains one, or more, EEG electrodes, an amplifier,and a local radio transmitter. A stimulus device may optionally be placed on each subject, such as an audio generator in the form of an ear plug, which produces a series of xe2x80x9cclickxe2x80x9d sounds. The subject""s brain waves are detected, amplified and modulate the transmitter""s carrier wave. A hand-held radio receiver receives the radio waves, demodulates them and converts them into audio tones. The receiver may have an array of LED (Light Emitting Diodes) which blink depending on the power and frequency composition of the brain wave signal. Power ratios in the frequencies of audio or somatosensory stimuli are similarly encoded. With the proper training, brain wave modulated tone signals can be immediately recognized as being generated by an intact brain or an injured brain. A physician or medical aide who is properly trained to use the Brain Stethoscope may determine, either by reading the LCD screen, listening to the audio tones, or by looking at the blinking LEDs, whether the patient""s brain function is abnormal and may evaluate the functional state of various levels of the patient""s nervous system.
Another embodiment, called xe2x80x9cVersion 3xe2x80x9d, uses a headband (or patch) and a hand-held receiver. The headband has 2-16 EEG electrodes, an amplifier for each electrode, an A/D (Analog/Digital) converter and a local radio transmitter. The transmitter broadcasts an FM or AM carrier which is modulated by the digital data, from the A/D converter, representing the subject""s brain waves. The hand-held receiver performs the functions of analyzing the brain waves and stimulating the subject. It includes a display and a microprocessor board. The type of brain wave analysis and stimulation may be the same in Version 1.
In another embodiment, called xe2x80x9cVersion 4xe2x80x9d, the EEG device has a single electrode on a headband or an adhesive patch which is placed on a person""s head to detect brain waves which are amplified and transmitted by a micro-transmitter to a microprocessor within a hand-held receiver. The microprocessor analyzes the power spectrum of the brain waves by comparison to predetermined norms, or by various ratios of power in different frequency bands. Version 4 preferably also includes a second patch having an EKG electrode and amplifier. Either or both patches may carry an A/D converter and microtransmitter, the second patch being placed on the skin above the left collarbone.
The hand-held receiver may have LEDs, or a display panel, which displays the results of the analysis, or an audio output.
In xe2x80x9cVersion 5xe2x80x9da single electrode is placed preferably midway between the ears. A patch containing the electrode also has an amplifier, an A/D converter, microprocessor and a display. The microprocessor analyzes the digital data and indicates if the subject""s brain waves are normal or abnormal. This Version 5 may be especially applicable in a battlefield situation.
The invention may be especially useful in cases of an emergency, for example, a wartime or peacetime explosion/disaster situation where a large number of people are injured or dead. The portable EEG device analyzes the power spectrum of brain waves to assist evaluating the degree of injury. By utilizing the portable EEG device, medical personnel may, for example, quickly divide patients into four categories: dead, seriously injured who must be moved to a hospital immediately, injured who can be moved to a hospital later, and injured, who should not be moved without special precautions.
One advantage of the portable EEG device is that it allows personnel at the scene of an emergency to determine almost instantly whether a person is alive but suffering from concussion; is having an ischemic stroke or is suffering intracerebral bleeding; if the person is dead or in coma; whether the patient has brainstem or spinal injury; or if the patient does not have a heartbeat. The device may be utilized by medical personnel in the field, ambulance medical personnel, firemen and policemen as well as other emergency room personnel, and may be relatively simple to use and low in cost. The instrument, when used in emergency vehicles, such as firetrucks and ambulances, preferably has a built-in cellular telephone which automatically dials-up or otherwise transmits its data to a neurometric computer, for example, at a hospital. Thus, while providing immediate automatic evaluation of patient""s brain state at the emergency site, it can transmit a series of brain measurements which are continuously updated to construct a xe2x80x9cstate trajectoryxe2x80x9d for remote evaluation by qualified specialists.